In modern communications systems, low phase noise oscillators are required as an integral part of the process of transporting data. While ever increasing data rates are employed, it becomes more and more difficult to meet the requirements for low phase noise. In many applications, the requirement for low phase noise has been met by means of oscillators with fixed frequencies or narrow band tuning range which utilizes some form of a resonant tank circuit of high quality factor (Q). The tank circuit limits the noise bandwidth of the oscillator circuit. In applications where a wider tuning range is needed, it is possible to use a multiple of such oscillators with overlapping tuning ranges. Such arrangements, however, are cumbersome and an alternative class of broad tuning range low noise integrated oscillator is desirable.
U.S. Pat. No. 5,371,475 granted to A. K. D. Brown on Dec. 6, 1994 describes the principles of operation of a class of low noise oscillators, which are known as gyrators. The principles of a conventional gyrator is fully described in the patent. U.S. Pat. No. 5,483,195 granted to A. K. D. Brown on Jan. 9, 1996 describes means of obtaining a broad tuning range for a gyrator oscillator which is independent of process and temperature variations. The prior gyrator needs improvement on achievement of broad tuning range concurrently with low phase noise, for some applications. A paper by A. K. D. Brown entitled "An integrated low power microwave VCO with sub-picosecond phase jitter", IEEE 96CH35966, IEEE BCTM 10.3, pp. 165-168 describes phase noise analysis of gyrators.